Methods of changing the visible light transmittance of coated articles and coated articles made thereby

ABSTRACT

A method is provided for changing the visible light transmittance of a coated article having a functional coating having at least one anti-reflective material and at least one infrared reflective material. The anti-reflective material includes an alloying material capable of combining or alloying with the infrared reflective material. A protective coating is deposited over the functional coating to prevent or retard the diffusion of atmospheric gas and/or vapor into the functional coating. The coated article is heated to a temperature sufficient to cause at least some of the alloying material to combine with at least some of the infrared reflective material to form a substance having a different visible light transmittance than the infrared reflective material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.10/422,096, filed Apr. 24, 2003, which was a continuation-in-part ofU.S. application Ser. No. 10/397,001 filed Mar. 25, 2003 (now U.S. Pat.No. 7,311,961), which was a continuation-in-part of U.S. applicationSer. No. 10/133,805 filed Apr. 25, 2002 (now abandoned), which was acontinuation-in-part of U.S. application Ser. No. 10/007,382 filed Oct.22, 2001 (now U.S. Pat. No. 6,869,644), which claimed priority to U.S.Provisional Application 60/242,543, filed Oct. 24, 2000, all of whichapplications are herein incorporated by reference in their entirety.This application is related to U.S. patent application Ser. No.11/085,330, filed Jun. 17, 2005 (herein incorporated by reference); U.S.patent application Ser. No. 11/941,208, filed Nov. 16, 2007; U.S. patentapplication Ser. No. 11/752,501, filed May 23, 2007; U.S. patentapplication Ser. No. 10/816,519, filed Apr. 1, 2004 (now U.S. Pat. No.7,232,615); U.S. patent application Ser. No. 10/422,095, filed Apr. 24,2003 (now U.S. Pat. No. 6,962,759); and U.S. patent application Ser. No.10/422,094, filed Apr. 24, 2003 (now U.S. Pat. No. 6,916,542).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to coated articles, e.g., coatedautomotive transparencies, and to methods of changing the visible lighttransmittance of the coated articles.

2. Description of the Currently Available Technology

It is known to reduce the heat build-up in the interior of a vehicle byproviding a laminated windshield having two glass plies with an infrared(IR) or ultraviolet (UV) attenuating solar control coating positionedbetween the plies. The plies protect the solar control coating frommechanical and/or chemical damage. These conventional windshields aregenerally made by shaping and annealing two flat glass “blanks” (one ofwhich has the solar control coating deposited thereon) to form twoshaped, annealed glass plies and then securing the glass plies togetherwith a plastic interlayer. Because conventional solar control coatingsinclude metal layers that reflect heat, the glass blanks are typicallyheated and shaped as “doublets”, i.e., the blanks are positioned one ontop of another during heating and shaping with the functional coatingsandwiched between the glass blanks to prevent uneven heating andcooling, which can affect the final shape of the plies. Examples oflaminated automotive windshields and methods of making the same aredisclosed in U.S. Pat. Nos. 4,820,902; 5,028,759; and 5,653,903.

The heatability of the doublet is generally limited by the ability ofthe functional coating to withstand the heat treatment without adverselydegrading. By “heatability” is meant the maximum temperature and/ormaximum time at a particular temperature to which the coated substratecan be heated without degradation of the functional coating. Suchdegradation can affect the physical and/or optical properties of thecoating, such as solar energy reflection and/or transmission. Suchdegradation can be caused, for example, by oxidation of variousmetal-containing layers in the functional coating. For example,functional coatings containing metal layers can be sensitive to oxygenin that there can be some change, e.g., decrease, in the optical and/orsolar control properties of the functional coating when the coatedsubstrate is heat treated, such as by heating, bending, annealing, ortempering, for use in a motor vehicle transparency or window or visionpanel, or for use in residential or commercial windows, panels, doors,or appliances.

It would also be advantageous to provide a solar control coating onother automotive transparencies, such as sidelights, back lights,sunroofs, moon roofs, etc. However, the processes of making laminatedwindshields are not easily adapted to making other types of laminatedand/or non-laminated automotive transparencies. For example,conventional automotive sidelights are usually made from a single glassblank that is individually heated, shaped, and tempered to a desiredcurvature dictated by the dimensions of the vehicle opening into whichthe sidelight is to be installed. A problem posed in making sidelightsnot encountered when making windshields is the problem of individuallyheating glass blanks having a heat-reflecting solar control coating.

Additionally, if the sidelight is positioned such that the coating is onthe surface of the sidelight facing away from the vehicle (the outersurface), the coating is susceptible to mechanical damage from objectshitting the coating and to chemical damage from acid rain or car washdetergents. If the coating is on the surface of the sidelight facing theinterior of the vehicle (the inner surface), the coating is susceptibleto mechanical damage from being touched by the vehicle occupants or frombeing rolled up and down in the window channel, and to chemical damagefrom contact with conventional glass cleaners. Additionally, if thecoating is a low emissivity coating it can promote a greenhouse effecttrapping heat inside the vehicle.

While it is known to reduce chemical damage or corrosion to a coating byovercoating with a chemically resistant material, these overcoats aretypically applied as thin as possible so as not to adversely affect theoptical characteristics (e.g., color, reflectance, and transmittance) ofthe underlying coating and so as not to significantly increase theemissivity of the underlying coating. Such thin overcoats typically donot meet the durability requirements for shipping, processing, or enduse of conventional coated automotive transparencies, which are easilydamaged and continuously exposed to the environment. Additionally, suchthin overcoats would not alleviate the greenhouse effect problemdiscussed above. Examples of conventional overcoats are disclosed inU.S. Pat. Nos. 4,716,086; 4,786,563; 5,425,861; 5,344,718; 5,376,455;5,584,902; and 5,532,180.

Therefore, it would be advantageous to provide a method of making anarticle, e.g., a laminated or non-laminated automotive transparency, orpanel, or sheet having a functional coating that reduces or eliminatesat least some of the problems discussed above.

Additionally, some areas of an automobile, such as rear sidelights, moonroofs, sunroofs, and the like, typically utilize so-called privacyglass. By “privacy glass” is meant glass having a lower visible lighttransmission than the windshield and/or front sidelights. Typically,privacy glass has a visible light transmittance of less than 50% andappears dark or black in color. Conventional privacy glass can be formedby adding colorants to the glass batch materials to color or shade theresultant glass article. While decreasing visible light transmittance,conventional privacy glass typically does not provide significant solarradiation reflective properties. Therefore, it would also beadvantageous to provide a method of making a coated article, e.g.,useful as a privacy glass. It would further be advantageous to provide amethod of providing an article of a desired color or shade. It wouldalso be advantageous to provide a method of preventing color and/orchemical changes to coatings upon heating.

SUMMARY OF THE INVENTION

A method is provided for changing the visible light transmittance of acoated article. The method includes providing a substrate having afunctional coating, with the functional coating comprising at least oneanti-reflective material and at least one infrared reflective material.The he anti-reflective material includes an alloying material capable ofcombining with the infrared reflective material. A protective coating isdeposited over at least a portion of the functional coating. Theprotective coating prevents or retards the diffusion of atmospheric gasand/or vapor, e.g., oxygen, into the functional coating. The coatedarticle is heated to a temperature sufficient to cause at least some ofthe alloying material to combine with at least some of the infraredreflective material to form a combination having a different visiblelight transmittance than the infrared reflective material.

Another method of making a coated article comprises providing asubstrate having a functional coating, with the functional coatingcomprising at least one anti-reflective layer and at least one infraredreflective layer. The anti-reflective layer includes an alloyingmaterial capable of combining with the material of the infraredreflective layer. An alloy prevention layer is deposited adjacent theinfrared reflective layer. The alloy prevention layer is configured toprevent or reduce combination of the infrared reflective material withthe alloying material. A protective coating can be deposited over atleast a portion of the functional coating.

A coated article comprises a substrate and a functional coatingdeposited over at least a portion of the substrate. The functionalcoating comprises at least on anti-reflective layer. At least one alloyprevention layer is deposited over at least a portion of theanti-reflective layer. At least one infrared reflective layer isdeposited over at least a portion of the alloy prevention layer. Theanti-reflective layer includes an alloying material capable of combiningwith the infrared reflective layer. The article further includes aprotective coating deposited over at least a portion of the infraredreflective layer.

Another coated article comprises a substrate and a functional coatingdeposited over at feast a portion of the substrate. The functionalcoating comprises an anti-reflective layer and an infrared reflectivelayer deposited over at least a portion of the anti-reflective layer.The anti-reflective layer contains a material capable of alloying withthe material of the infrared reflective layer. A protective coating isdeposited over at least a portion of the infrared reflective layer

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side, sectional view (not to scale) of an edge portion of alaminated automotive transparency, e.g., a sidelight, incorporatingfeatures of the invention;

FIG. 2 is a perspective, partially broken view of an apparatus (withportions removed for clarity) for producing glass blanks G (coated oruncoated) in the practice of the invention;

FIG. 3 is a side, sectional view (not to scale) of a portion of amonolithic article incorporating features of the invention;

FIG. 4 is a graph showing Taber abrasion test results for substrateshaving a protective coating of the invention compared to substrateswithout the protective coating;

FIG. 5 is a graph of the average haze for selected substrates of FIG. 4;

FIG. 6 is a graph of emissivity value versus coating thickness forsubstrates having a protective coating of the invention;

FIG. 7 is a graph showing Taber abrasion test results for substrateshaving a protective coating of the invention;

FIG. 8 is a bar graph showing the effects of heat treatment and coatingthickness on Taber abrasion for coated substrates having a protectivecoating of the invention;

FIG. 9 is a partial, sectional view (not to scale) of a monolithicarticle useful for privacy glass applications; and

FIG. 10 is a partial, sectional view (not to scale) of a monolithicarticle having a higher visible light transmittance than the article ofFIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, spatial or directional terms, such as “left”, “right”,“inner”, “outer”, “above”, “below”, “top”, “bottom”, and the like,relate to the invention as it is shown in the drawing figures. However,it is to be understood that the invention may assume various alternativeorientations and, accordingly, such terms are not to be considered aslimiting. Further, as used herein, all numbers expressing dimensions,physical characteristics, processing parameters, quantities ofingredients, reaction conditions, and the like, used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical value should at least be construedin light of the number of reported significant digits and by applyingordinary rounding techniques. Moreover, all ranges disclosed herein areto be understood to encompass the beginning and ending range values andany and all subranges subsumed therein. For example, a stated range of“1 to 10” should be considered to include any and all subranges between(and inclusive of) the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, e.g., 5.5 to 10. The terms“flat” or “substantially flat” substrate refer to a substrate that issubstantially planar in form; that is, a substrate lying primarily in asingle geometric plane, which substrate, as would be understood by oneskilled in the art, can include slight bends, projections, ordepressions therein. Further, as used herein, the terms “formed over”,“deposited over”, or “provided over” mean formed, deposited, or providedon but not necessarily in contact with the surface. For example, acoating layer “formed over” a substrate does not preclude the presenceof one or more other coating layers or films of the same or differentcomposition located between the formed coating layer and the substrate.For instance, the substrate can include a conventional coating such asthose known in the art for coating substrates, such as glass or ceramic.All documents referred to herein are to be understood to be incorporatedby reference in their entirety. As used herein, the terms “polymer” or“polymeric” refer to oligomers, homopolymers, copolymers, andterpolymers, e.g., polymers formed from two or more types of monomers orpolymers.

As will be appreciated from the following discussion, the protective(e.g., barrier) coating of the invention can be utilized in making bothlaminated and non-laminated, e.g., single substrate, articles. As willbe appreciated from the following discussion, the protective or barriercoating of the invention can be utilized in making both laminated andnon-laminated, e.g., single ply, articles. By “protective coating” or“barrier coating” is meant a film, layer or coating formed from aprotective or barrier material and at a sufficient thickness to limitthe transmission of oxygen-containing gases through the coating. By“protective material” or “barrier material” is meant a material having alow permeability to oxygen-containing gases, such as air or water vapor.The material can exhibit a high resistance to the passage of oxygen orair or water vapor through the material. More suitable barrier materialhas limited cracking when it is in the form of a coating at theconditions of the invention and is substantially stable to oxygen atsuch conditions. As will be appreciated by one skilled in the coatingart, permeation through a material is a function of the thickness of thematerial. The barrier coating of the present invention exhibits acombination of relatively high resistance to both air and water vaporbut some applications do not require resistance to both. Therefore, lowpermeability to either air or water vapor is sufficient to qualify thecoating as a “barrier coating.” Embodiments of barrier coatings of thepresent invention intended primarily as oxygen barriers can exhibit anoxygen permeability of less than about 1.5, such as less than about 1.0,such as less than about 0.5 measured as cubic centimeters of oxygen gaspermeating a one-mil thick sample, 100 inches square over a 24-hourperiod under an oxygen partial pressure differential of one atmosphereat 23° C. and at a relative humidity of zero. The barrier coating can bestable to oxygen containing gasses so that the coating can withstandconditioning, such as heating to bend, sag, temper, or anneal, withminimal if any change in its oxygen barrier properties from those thatexisted before the conditioning step.

For use with laminated articles, the protective coating can usually bethinner than for non-laminated articles. The structural components and amethod of making an exemplary laminated article of the invention willfirst be described and then an exemplary monolithic article of theinvention will be described. By “monolithic” is meant having a singlestructural support or structural member, e.g., having a singlesubstrate. In the following discussion, the exemplary article (whetherlaminated or monolithic) is described as an automotive sidelight.However, the invention is not limited to automotive sidelights but maybe used with any articles, such as but not limited to, insulating glassunits, residential or commercial laminated windows (e.g., skylights), ortransparencies for land, air, space, above water and underwatervehicles, e.g. windshields, backlights, sun or moon roofs, just to namea few articles.

FIG. 1 illustrates a laminated article in the form of a sidelight 10incorporating features of the invention. The laminated sidelight 10includes a first substrate or ply 12 having an outer major surface 13and an inner major surface 14. By “ply” is meant a substrate that hasbeen bent to a desired shape or curvature and/or heat-treated, such asby annealing or tempering. A functional coating 16 can be formed over,e.g., on, at least a portion, preferably all, of the inner major surface14 in any conventional manner, such as but not limited to chemical vapordeposition, magnetron sputter vapor deposition, spray pyrolysis, just toname a few. As will be described in more detail, a barrier or protectivecoating 17 of the invention can be formed over, e.g., on, at least aportion, preferably all, of the functional coating 16 and aids not onlyin increasing mechanical and chemical durability but also providesimproved heating characteristics for bending and/or shaping the blank onwhich it is deposited. A polymeric layer 18 can be located between thefirst ply 12 and a second substrate or ply 20 having an inner majorsurface 22 and an outer major surface 23. In one non-limitingembodiment, the outer major surface 23 can face the exterior of thevehicle and the outer major surface 13 can face the interior of thevehicle. A conventional edge sealant 26 can be applied to the perimeterof the laminated sidelight 10 during and/or after lamination in anyconventional manner. A decorative band 90, e.g., an opaque, translucentor colored band, such as a ceramic band, can be provided on a surface ofat least one of the plies 12 and 20, for example, around the perimeterof one of the inner or outer major surfaces.

In the broad practice of the invention, the substrates used for firstply 12 and second ply 20 can be of any desired material having anydesired characteristics, such as opaque, translucent, or transparent tovisible light. By “transparent” is meant having a transmittance throughthe substrate of greater than 0% up to 100%. By “visible light” or“visible region” is meant electromagnetic energy in the range of 395nanometers (nm) to 800 nm. Alternatively, the substrate can betranslucent or opaque. By “translucent” is meant allowingelectromagnetic energy (e.g., visible light) to pass through thesubstrate but diffusing this energy such that objects on the side of thesubstrate opposite to the viewer are not clearly visible. By “opaque” ismeant having a visible light transmittance of 0%. Examples of suitablesubstrates include, but are not limited to, plastic substrates (such asacrylic polymers, such as polyacrylates; polyalkylmethacrylates, such aspolymethylmethacrylates, polyethylmethacrylates,polypropylmethacrylates, and the like; polyurethanes; polycarbonates;polyalkylterephthalates, such as polyethyleneterephthalate (PET),polypropyleneterephthalates, polybutyleneterephthalates, and the like;polysiloxane containing polymers; or copolymers of any monomers forpreparing these, or any mixtures thereof); metal substrates, such as butnot limited to galvanized steel, stainless steel, and aluminum; ceramicsubstrates; tile substrates; glass substrates; or mixtures orcombinations of any of the above. For example, the substrate can beconventional untinted soda-lime-silica-glass, i.e., “clear glass”, orcan be tinted or otherwise colored glass, borosilicate glass, leadedglass, tempered, untempered, annealed, or heat-strengthened glass. Theglass may be of any type, such as conventional float glass or flatglass, and may be of any composition having any optical properties,e.g., any value of visible radiation transmission, ultraviolet radiationtransmission, infrared radiation transmission, and/or total solar energytransmission. Types of glass suitable for the practice of the inventionare described, for example but not to be considered as limiting, in U.S.Pat. Nos. 4,746,347; 4,792,536; 5,240,886; 5,385,872; and 5,393,593. Theinvention is not limited by the thickness of the substrate. Thesubstrate can generally be thicker for typical architecturalapplications than for typical vehicle applications. In one embodiment,the substrate can be glass having a thickness in the range of 1 mm to 20mm, such as about 1 mm to 10 mm, such as 2 mm to 6 mm, such as 3 mm to 5mm. For forming a laminated automotive sidelight, the first and secondplies 12, 20 can be less than about 3.0 mm thick, such as less thanabout 2.5 mm thick, such as in the thickness range of about 1.0 mm toabout 2.1 mm. As described below, for monolithic articles the substratecan be thicker.

The substrate can have oxygen barrier properties, e.g., can be made of amaterial that prevents or limits the diffusion of oxygen through thesubstrate. Alternatively, another oxygen barrier coating (in addition tothe barrier coating 17 described below) can be formed over at least aportion of the substrate and the functional coating 16 can besubsequently formed over this other oxygen barrier coating. The otheroxygen barrier coating can be of any material to prevent or limit thediffusion of oxygen, such as but not limited to those described belowfor the protective coating 17.

The functional coating 16 can be of any desired type. As used herein,the term “functional coating” refers to a coating that modifies one ormore physical properties of the substrate over which it is deposited,e.g., optical, thermal, chemical or mechanical properties, and is notintended to be entirely removed from the substrate during subsequentprocessing. The functional coating 16 can have one or more functionalcoating layers or films of the same or different composition orfunctionality. As used herein, the term “film” refers to a coatingregion of a desired or selected coating composition. A “layer” cancomprise one or more “films” and a “coating” can comprise one or more“layers”.

For example, the functional coating 16 can be an electrically conductivecoating, such as, for example, an electrically conductive coating usedto make heatable windows as disclosed in U.S. Pat. Nos. 5,653,903 and5,028,759, or a single-film or multi-film coating used as an antenna.Likewise, the functional coating 16 can be a solar control coating. Asused herein, the term “solar control coating” refers to a coatingcomprised of one or more layers or films which affect the solarproperties of the coated article, such as but not limited to the amountof solar radiation, for example, visible, infrared, or ultravioletradiation incident on and/or passing through the coated article,infrared or ultraviolet absorption or reflection, shading coefficient,emissivity, etc. The solar control coating can block, absorb or filterselected portions of the solar spectrum, such as but not limited to theIR, UV, and/or visible spectrums. Examples of solar control coatingsthat can be used in the practice of the invention are found, for examplebut not to be considered as limiting, in U.S. Pat. Nos. 4,898,789;5,821,001; 4,716,086; 4,610,771; 4,902,580; 4,716,086; 4,806,220;4,898,790; 4,834,857; 4,948,677; 5,059,295; and 5,028,759, and also inU.S. patent application Ser. Nos. 09/058,440 and 60/355,912.

The functional coating 16 can also be a low emissivity coating thatallows visible wavelength energy, e.g., 395 nm to 800 nm, to betransmitted through the coating but reflects longer-wavelength solarinfrared energy. By “low emissivity” is meant emissivity less than 0.4,such as less than 0.3, such as less than 0.2, such as less than 0.1,e.g., less than or equal to 0.05. Examples of low emissivity coatingsare found, for example, in U.S. Pat. Nos. 4,952,423 and 4,504,109 andBritish reference GB 2,302,102. The functional coating 16 can be asingle layer coating or multiple layer coating and can include one ormore metals, non-metals, semi-metals, semiconductors, and/or alloys,compounds, composites, combinations, or blends thereof. For example, thefunctional coating 16 can be a single layer metal oxide coating, amultiple layer metal oxide coating, a non-metal oxide coating, ametallic nitride or oxynitride coating, or a non-metallic nitride oroxynitride coating, or a multiple layer coating.

Examples of suitable functional coatings for use with the invention arecommercially available from PPG industries, Inc. of Pittsburgh, Pa.under the SUNGATE® and SOLARBAN® families of coatings. Such functionalcoatings typically include one or more anti-reflective coating filmscomprising dielectric or anti-reflective materials, such as metal oxidesor oxides of metal alloys, which are transparent to visible light. Thefunctional coating can also include one or more infrared reflectivefilms comprising a reflective metal, e.g., a noble metal such as gold,copper or silver, or combinations or alloys thereof, and can furthercomprise a primer film or barrier film, such as titanium, as is known inthe art, located over and/or under the metal reflective layer. Thefunctional coating can have any desired number of infrared reflectivefilms, such as 1 or more silver layers, e.g., 2 or more silver layers,e.g., 3 or more silver layers.

Although not limiting to the invention, the functional coating 16 can bepositioned on one of the inner major surfaces 14, 22 of the laminate tomake the coating 16 less susceptible to environmental and mechanicalwear than if the functional coating 16 were on an outer surface of thelaminate. However the functional coating 16 could also be provided onone or both of the outer major surfaces 13 or 23. As shown in FIG. 1, aportion of the coating 16, e.g., about a 1 mm to 20 mm, such as 2 mm to4 mm wide area around the outer perimeter of the coated region, can beremoved or deleted in any conventional manner, e.g., by grinding priorto lamination or masking during coating, to minimize damage to thefunctional coating 16 at the edge of the laminate by weathering orenvironmental action during use. In addition, deletion could be done forfunctional performance, e.g., for antennas, heated windshields, or toimprove radio-wave transmission, and the deleted portion can be of anysize. For aesthetic purposes, a colored, opaque, or translucent band 90can be provided over any surface of the plies or the coatings, forexample over one or both surfaces of one or both of the plies, e.g.,around the perimeter of the outer major surface 13, to hide the deletedportion. The band 90 can be made of a ceramic material and may be firedonto the outer major surface 13 in any conventional manner.

The protective (barrier) coating 17 of the invention can be formed over,e.g., on, at least a portion, preferably all, of the outer surface ofthe functional coating 16. The protective coating 17, among otherthings, can raise the emissivity of the coating stack (e.g., thefunctional coating plus protective coating) to be greater than theemissivity of the functional coating 16 alone. By way of example, if thefunctional coating 16 has an emissivity value of 0.2, the addition ofthe protective coating 17 can raise the emissivity value of theresultant coating stack to an emissivity of greater than 0.2. In oneembodiment, the protective coating can increase the emissivity of theresulting coating stack by a factor of two or more over the emissivityof the functional coating alone (e.g., if the emissivity of thefunctional coating is 0.05, the addition of the protective layer canincrease the emissivity of the resulting coating stack to 0.1 or more),such as by a factor of five or more, e.g., by a factor of ten or more,e.g., by a factor of twenty or more. The protective coating can increasethe emissivity of the at least one functional coating and the at leastone deposited (protective) coating as a stack of coatings when thefunctional coating has an emissivity in the range from 0.02 to 0.30,more suitably 0.03 to 0.15, by a percentage that is from less than 10 to3,000 percent or within this range from 50 to 200 percent or 10 to 200percent or 200 to 1,000 percent or 1,000 to 3,000 percent. In anotherembodiment of the invention, the protective coating 17 can raise theemissivity of the resulting coating stack to be substantially the sameas the emissivity of the substrate on which the coating is deposited,e.g., within 0.2 of the emissivity of the substrate. For example, if thesubstrate is glass having an emissivity of about 0.84, the protectivecoating 17 can provide the coating stack with an emissivity in the rangeof 0.3 to 0.9, such as greater than 0.3, e.g., greater than 0.5, e.g.,greater than 0.6, e.g., in the range of 0.5 to 0.9. As will be describedbelow, increasing the emissivity of the functional coating 16 bydeposition of the protective coating 17 improves the heating and coolingcharacteristics of the coated ply 12 during processing. The protectivecoating 17 also protects the functional coating 16 from mechanical andchemical attack during handling, storage, transport, and processing.

In one embodiment, the protective coating 17 can have an index ofrefraction (i.e., refractive index) that is substantially the same asthat of the ply 12 to which it is laminated. For example, if the ply 12is glass having an index of refraction of 1.5, the protective coating 17can have an index of refraction of less than 2, such as 1.4 to 1.8, suchas 1.3 to 1.8, e.g., 1.5±0.2.

The protective coating 17 can be of any desired thickness. In oneexemplary laminated article embodiment, the protective coating 17 canhave a thickness in the range of 100 Å to 50,000 Å, such as 500 Å to50,000 Å, e.g., 500 Å to 10,000 Å, such as 100 Å to 2,000 Å. In othernon-limiting embodiments, the protective coating 17 can have a thicknessin the range of 100 Å to 10 microns, such as 101 Å to 1,000 Å, or 1,000Å to 1 micron, or 1 micron to 10 microns, or 200 Å to 1,000 Å. Further,the protective coating 17 can be of non-uniform thickness across thesurface of the functional coating 17. By “non-uniform thickness” ismeant that the thickness of the protective coating 17 can vary over agiven unit area, e.g., the protective coating 17 can have high and lowspots or areas.

The protective coating 17 can be of any desired material or mixture ofmaterials. In one exemplary embodiment, the protective coating 17 caninclude one or more metal oxide materials, such as but not limited to,aluminum oxide, silicon oxide, or mixtures thereof. For example, theprotective coating can be a single coating layer comprising in the rangeof 0 wt. % to 100 wt. % alumina and/or 0 wt. % to 100 wt. % silica, suchas 5 wt. % to 100 wt. % alumina and 95 wt. % to 0 wt. % silica, such as10 wt. % to 90 wt. % alumina and 90 wt. % to 10 wt. % silica, such as 15wt. % to 90 wt. % alumina and 85 wt. % to 10 wt. % silica, such as 50wt. % to 75 wt. % alumina and 50 wt. % to 26 wt. % silica, such as 60wt. % to 70 wt. % alumina and 50 wt. % to 30 wt. % silica, such as 35wt. % to 100 wt. % alumina and 65 wt. % to 0 wt. % silica, e.g., 70 wt.% to 90 wt. % alumina and 10 wt. % to 30 wt. % silica, e.g., 75 wt. % to85 wt. % alumina and 15 wt. % to 26 wt. % of silica, e.g., 88 wt. %alumina and 12 wt. % silica, e.g., 65 wt. % to 75 wt. % alumina and 25wt. % to 36 wt. % silica, e.g., 70 wt. % alumina and 30 wt. % silica,e.g., 60 wt. % to less than 75 wt. % alumina and greater than 25 wt. %to 40 wt. % silica. Other materials, such as aluminum, chromium,hafnium, yttrium, nickel, boron, phosphorous, titanium, zirconium,and/or oxides thereof, can also be present, such as to adjust therefractive index of the coating 17. In one embodiment, the refractiveindex of the protective coating can be in the range of 1 to 3, such as 1to 2, such as 1.4 to 2, such as 1.4 to 1.8.

Alternatively, the protective coating 17 can be a multilayer coatingformed by separately formed layers of metal oxide materials, such as butnot limited to a bilayer formed by one metal oxide containing layer(e.g., a silica and/or alumina containing first layer) formed overanother metal oxide containing layer (e.g., a silica and/or aluminacontaining second layer). The individual layers of the multilayerprotective coating 17 can be of any desired thickness.

In one embodiment, the protective coating 17 can comprise a first layerformed over the functional coating and a second layer formed over thefirst layer. In one non-limiting embodiment, the first layer cancomprise alumina or a mixture or alloy comprising alumina and silica.For example, the first layer can comprise a silica/alumina mixturehaving greater than 5 wt. % alumina, such as greater than 10 wt. %alumina, such as greater than 15 wt. % alumina, such as greater than 30wt. % alumina, such as greater than 40 wt. % alumina, such as 50 wt. %to 70 wt. % alumina, such as in the range of 70 wt. % to 100 wt. %alumina and 30 wt. % to 0 wt. % silica. In one non-limiting embodiment,the first layer can have a thickness in the range of greater than 0 Å to1 micron, such as 50 Å to 100 Å, such as 100 Å to 250 Å, such as 101 Åto 250 Å, such as 100 Å to 150 Å, such as greater than 100 Å to 125 Å.The second layer can comprise silica or a mixture or ahoy comprisingsilica and alumina.

For example, the second layer can comprise a silica/alumina mixturehaving greater than 40 wt. % silica, such as greater than 50 wt. %silica, such as greater than 60 wt. % silica, such as greater than 70wt. % silica, such as greater than 80 wt. % silica, such as in the rangeof 80 wt. % to 90 wt. % silica and 10 wt. % to 20 wt. % alumina, e.g.,85 wt. % silica and 15 wt. % alumina. In one non-limiting embodiment,the second layer can have a thickness in the range of greater than 0 Åto 2 microns, such as 50 Å to 5,000 Å, such as 50 Å to 2,000 Å, such as100 Å to 1,000 Å, such as 300 Å to 500 Å, such as 350 Å to 400 Å. Asdescribed below, the presence of the protective coating 17 can improvethe heatability of the functionally coated substrate.

The polymeric layer 18 can include any polymeric material. The“polymeric material” can comprise one polymeric component or cancomprise a mixture of different polymeric components, such as but notlimited to one or more plastic materials, such as but not limited to oneor more thermoset or thermoplastic materials. The polymeric layer 18 canadhere the plies together. Useful thermoset components includepolyesters, epoxides, phenolics, and polyurethanes such as reactioninjected molding urethane (RIM) thermoset materials and mixturesthereof. Useful thermoplastic materials include thermoplasticpolyolefins such as polyethylene and polypropylene, polyamides such asnylon, thermoplastic polyurethanes, thermoplastic polyesters, acrylicpolymers, vinyl polymers, polycarbonates,acrylonitrile-butadiene-styrene (ABS) copolymers, EPDM rubber,copolymers and mixtures thereof.

Suitable acrylic polymers include copolymers of one or more of acrylicacid, methacrylic acid and alkyl esters thereof, such as methylmethacrylate, ethyl methacrylate, hydroxyethyl methacrylate, butylmethacrylate, ethyl acrylate, hydroxyethyl acrylate, butyl acrylate and2-ethylhexyl acrylate. Other suitable acrylics and methods for preparingthe same are disclosed in U.S. Pat. No. 5,196,485.

Useful polyesters and alkyds can be prepared in a known manner bycondensation of polyhydric alcohols, such as ethylene glycol, propyleneglycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol,trimethylolpropane and pentaerythritol, with polycarboxylic acids suchas adipic acid, maleic acid, fumaric acid, phthalic acids, trimelliticacid or drying oil fatty acids. Examples of suitable polyester materialsare disclosed in U.S. Pat. Nos. 5,739,213 and 5,811,198.

Useful polyurethanes include the reaction products of polymeric polyolssuch as polyester polyols or acrylic polyols with a polyisocyanate,including aromatic diisocyanates such as 4,4′-diphenylmethanediisocyanate, aliphatic diisocyanates such as 1,6-hexamethylenediisocyanate, and cycloaliphatic diisocyanates such as isophoronediisocyanate and 4,4′-methylene-bis(cyclohexyl isocyanate). The term“polyurethane” as used herein is intended to include polyurethanes aswell as polyureas, and poly(urethane-ureas).

Suitable epoxy-functional materials are disclosed in U.S. Pat. No.5,820,987.

Useful vinyl resins include polyvinyl acetyl, polyvinyl formal, andpolyvinyl butyral.

The polymeric layer 18 can have any desired thickness, e.g., in onenon-limiting embodiment for polyvinyl butyral the thickness can be inthe range of 0.50 mm to about 0.80 mm, such as 0.76 mm. The polymericmaterial can have any desired refractive index. In one embodiment, thepolymeric material has a refractive index in the range of 1.4 to 1.7,such as 1.5 to 1.6.

The protective coating 17 can have an index of refraction that issubstantially the same as the refractive index of the polymeric layer 18material. By “substantially the same” refractive index is meant that therefractive index of the protective coating material and the polymericlayer material are the same or sufficiently close that little or noundesirable optical effects, such as undesirable changes in color,reflectance, or transmittance are caused by the presence of theprotective coating 17. In effect, the protective coating 17 behavesoptically as if it were a continuation of the polymeric layer material.The presence of the protective coating 17 preferably does not cause theintroduction of an optically undesirable interface between theprotective coating 17 and the polymeric layer 18. In one embodiment, theprotective coating 17 and polymeric layer 18 can have indices ofrefraction that are within ±0.2 of each other, such as within ±0.1, suchas within ±0.05. By providing that the refractive index of theprotective coating material is the same as or substantially the same asthe refractive index of the polymeric layer material, the presence ofthe protective coating 17 does not adversely impact upon the opticalproperties of the laminated article compared to the optical propertiesof the laminated article without the protective coating 17. For example,if the polymeric layer 18 comprises polyvinyl butyral having an index ofrefraction of 1.5, the protective coating 17 can be selected or formedto have an index of refraction of less than 2, such as 1.3 to 1.8, e.g.,1.5±0.2.

An exemplary method of making a laminated sidelight 10 utilizingfeatures of the invention will now be discussed.

A first substrate and a second substrate are provided. The first andsecond substrates can be flat glass blanks having a thickness of about1.0 mm to 6.0 mm, typically about 1.0 mm to about 3.0 mm, such as about1.5 mm to about 2.3 mm. A functional coating 16 can be formed over atleast a portion of a major surface of the first glass substrate, forexample, the major surface 14. The functional coating 16 can be formedin any conventional manner, such as but not limited to, magnetronsputter vapor deposition (MSVD), pyrolytic deposition such as chemicalvapor deposition (CVD), spray pyrolysis, atmospheric pressure CVD(APCVD), low-pressure CVD (LPCVD), plasma-enhanced CVD (PEVCD), plasmaassisted CVD (PACVD), or thermal evaporation by resistive orelectron-beam heating, cathodic arc deposition, plasma spray deposition,wet chemical deposition (e.g., sol-gel, mirror silvering, etc.), or anyother desired manner. For example, the functional coating 16 can beformed over the first substrate after the first substrate is cut to adesired dimension. Alternatively, the functional coating 16 can beformed over a glass sheet before it is processed and/or over a floatglass ribbon supported on a bath of molten metal, e.g., tin, in aconventional float chamber by one or more conventional CVD coaterspositioned in the float chamber. Upon exiting the float chamber, theribbon can be cut to form the coated first substrate.

Alternatively, the functional coating 16 can be formed over the floatglass ribbon after the ribbon exits the float chamber. For example, U.S.Pat. Nos. 4,584,206, 4,900,110, and 5,714,199 disclose methods andapparatus for depositing a metal-containing film on the bottom surfaceof a glass ribbon. Such a known apparatus can be located downstream of amolten tin bath in the float glass process to provide a functionalcoating on the bottom of the glass ribbon, i.e., the side of the ribbonthat was in contact with the molten metal. Still further, the functionalcoating 16 can be formed over the first substrate by MSVD after thesubstrate has been cut to a desired dimension.

A protective coating 17 of the invention can be formed over at least aportion of the functional coating 16. The protective coating 17 providesseveral processing advantages in making the laminated article. Forexample, the protective coating 17 can protect the functional coating 16from mechanical and/or chemical attack during handling, transport,storage, and processing. Additionally, as described below, theprotective coating 17 can facilitate individual heating and cooling ofthe functionally coated blank by increasing the emissivity of theresulting coating stack. While topcoats have been applied ontofunctional coatings in the past to help protect the functional coatingfrom chemical and mechanical attack during processing, these topcoatswere made as thin as possible so as not to impact upon the aesthetic orsolar control properties of the functional coating, such as the coatingemissivity. Conversely, in the present invention, the protective coating17 can be made sufficiently thick so as to raise the emissivity of thecoating stack. Further, by substantially matching the index ofrefraction of the protective coating 17 to that of the polymeric layer18 material (and/or the substrate to which it is laminated), there islittle or no adverse impact by the presence of the protective coating 17upon the aesthetic and/or optical characteristics of the laminatedarticle 10.

If the functional coating 16 is a low emissivity coating having one ormore infrared reflecting metal layers, the addition of the protectivecoating 17 to raise the emissivity of the coating stack reduces thethermal infrared reflecting characteristics of the functional coating16. However, the coating stack remains solar infrared reflective.

The protective coating 17 can be formed in any conventional manner, suchas but not limited to those described above for applying the functionalcoating, e.g., in-bath or out-of-bath CVD, MSVD, or sol-gel, just toname a few. For example, the substrate with the functional coating canbe directed to a conventional MSVD coating apparatus having one or moremetal electrodes, e.g., cathodes, that can be sputtered in anoxygen-containing atmosphere to form a metal oxide protective coating.In one non-limiting embodiment, the MSVD apparatus can include one ormore cathodes of aluminum, silicon, or mixtures or alloys of aluminum orsilicon. The cathodes can be for example, 5 wt. % to 100 wt. % aluminumand 95 wt. % to 0 wt. % silicon, such as 10 wt. % to 100 wt. % aluminumand 90 wt. % to 0 wt. % silicon, such as 35 wt. % to 100 wt. % aluminumand 0 wt. % to 65 wt. % silicon, e.g., 50 wt. % to 80 wt. % aluminum and20 wt. % to 50 wt. % silicon, e.g., 70 wt. % aluminum and 30 wt. %silicon. Additionally, other materials or dopants, such as aluminum,chromium, hafnium, yttrium, nickel, boron, phosphorous, titanium, orzirconium, can also be present to facilitate sputtering of thecathode(s) and/or to affect the refractive index or durability of theresultant coating. As described above, the protective coating 17 can beformed as a single layer comprising one or more metal oxide materials oras a multilayer coating having two or more separate layers, with eachseparate layer comprising one or more metal oxide materials. Theprotective coating 17 can be applied in a sufficient amount or to asufficient thickness to raise the emissivity of the coating stack overthat of just the functional coating alone. In one embodiment, theprotective coating can be applied to a thickness in the range of 100 Åto 50,000 Å and/or to raise the emissivity of the coating stack togreater than or equal to about 0.3, e.g., greater than or equal to 0.4,e.g., greater than or equal to 0.5.

The functional coating 16 and/or protective coating 17 can be applied tothe flat substrate or to the substrate after the substrate has been bentand shaped to a desired contour.

The coated first substrate and uncoated second substrate can be cut toprovide a first, coated ply and a second, uncoated ply, respectively,each having a desired shape and desired dimensions. The coated anduncoated plies can be seamed, washed, bent, and shaped to a desiredcontour to form the first and second plies 12 and 20, respectively, tobe laminated. As can be appreciated by one of ordinary skill in the art,the overall shapes of the coated and uncoated blanks and plies dependupon the particular vehicle into which they will be incorporated, sincethe final shape of a sidelight differs between different automotivemanufacturers.

The coated and uncoated blanks can be shaped using any desired process.For example, the blanks can be shaped using the “RPR” process disclosedin U.S. Pat. No. 5,286,271 or the modified RPR process disclosed in U.S.patent application Ser. No. 09/512,852. FIG. 2 shows an additional RPRapparatus 30 suitable for the practice of the invention and includes afurnace 32, e.g., a radiant heat furnace or tunnel Lehr, having afurnace conveyor 34 comprised of a plurality of spaced furnace conveyorrolls 36. Heaters, such as radiant heater coils, can be positioned aboveand/or below the furnace conveyor 34 along the length of the furnace 32and can be controlled to form heating zones of different temperaturealong the length of the furnace 32.

A shaping station 50 can be located adjacent the discharge end of thefurnace 32 and can include a lower mold 51 having a vertically movableflexible ring 52 and a shaping station conveyor 54 having a plurality ofrolls 56. An upper vacuum mold 58 having a removable or reconfigurableshaping surface 60 of a predetermined shape can be located above thelower mold 51. The vacuum mold 58 can be movable via a shuttlearrangement 61.

A transfer station 62 having a plurality of shaped transfer roils 64 canbe boated adjacent a discharge end of the shaping station 50. Thetransfer rolls 64 can have a transverse elevational curvaturecorresponding substantially to the transverse curvature of the shapingsurface 60.

A tempering or cooling station 70 can be located adjacent a dischargeend of the transfer station 62 and can include a plurality of rolls 72to move the blanks through the station 70 for cooling, tempering, and/orheat strengthening. The rolls 72 can have a transverse elevationalcurvature substantially the same as that of the transfer rolls 64.

In the past, heating functionally coated blanks (substrates) presenteddifficulties due to the heat reflectance of the functional coating 16,which caused uneven heating of the coated and uncoated sides of theblank. U.S. patent application Ser. No. 09/512,852 discloses a method ofovercoming this problem by modifying the RPR heating process to supplyheat primarily toward the non-functionally coated surface of the blank.In the present invention, this problem is addressed by deposition of theemissivity increasing protective coating 17, which allows the same orsubstantially the same heating process to be used both for thefunctionally coated and non-functionally coated blanks.

As shown in FIG. 2, the first blank 80 with the coating stack (e.g.,functional coating 16 and protective coating 17) and thenon-functionally coated second blank 82 can be individually heated,shaped, and cooled prior to lamination. By “individually heated” ismeant that the blanks are not stacked one on top of the other duringheating. In one embodiment, the first blank 80 is placed on the furnaceconveyor 34 with the protective coating 17 facing downwardly, i.e., incontact with the furnace conveyor rolls 36, during the heating process.The presence of the higher emissivity protective coating 17 reduces theproblem of heat reflectance by the metal layers of the functionalcoating 16 and promotes more even heating of the coated and uncoatedsides of the first blank 80. This helps prevent curling of the firstblank 80 common in prior heating processes. In one exemplary embodiment,the blanks are heated to a temperature of about 640° C. to 704° C.during a period of about 10 mins to 30 mins.

At the end of the furnace 32, the softened glass blanks, whether coated80 or non-coated 82, are moved from the furnace 32 to the shapingstation 50 and onto the lower mold 51. The lower mold 51 moves upwardly,lifting the glass blank to press the heat-softened glass blank againstthe shaping surface 60 of the upper mold 58 to conform the glass blankto the shape, e.g., curvature, of the shaping surface 60. The uppersurface of the glass blank is in contact with the shaping surface 60 ofthe upper mold 55 and is held in place by vacuum.

The shuttle arrangement 61 is actuated to move the upper vacuum mold 58from the shaping station 50 to the transfer station 62, where the vacuumis discontinued to release the shaped glass blank onto the curvedtransfer rolls 64. The transfer rolls 64 move the shaped glass blankonto the rolls 72 and into the cooling station 70 for tempering or heatstrengthening in any convenient manner. In the cooling station 70, airis directed from above and below the shaped glass blanks to temper orheat strengthen the glass blanks to form the first and second plies 12and 20. The presence of the high emissivity protective coating 17 alsopromotes more even cooling of the coated blank 80 in the cooling station70.

In another embodiment, the coated and uncoated blanks can be heatedand/or shaped as doublets. In one embodiment, the coated and uncoatedblanks can be positioned such that the functional coating 16 with theprotective coating 17 is located between the two blanks. The blanks canthen be heated and/or shaped in any conventional manner. It is believedthat the protective coating 17 acts as an oxygen barrier to reduce orprevent oxygen passing into the functional coating 16 where the oxygencould react with components of the functional coating 16, such as butnot limited to metals (e.g., silver), to degrade the functional coating16. In one conventional method, the doublet can be placed on a supportand heated to sufficient temperature to bend or shape the blanks to adesired final contour. In the absence of the protective coating 17,typical functionally coated blanks cannot withstand a heating cyclehaving heating above about 1100° F. (593° C.) for more than about twominutes (with heating above 900° F. (482° C.) for more than about sixminutes during the heating cycle) without degradation of the functionalcoating 16. Such degradation can take the form of a hazy or yellowishappearance with a decrease in visible light transmission of 10% or more.Metal layers in the functional coating 16, such as silver layers, canreact with oxygen diffusing into the functional coating 16 or withoxygen present in the functional coating 16. However, it is believedthat utilizing the protective coating 17 will permit the functionallycoated blank to withstand a heating cycle with heating to a temperatureof 1100° F. (593° C.) or more for a period of five to fifteen minutes,such as five to ten minutes, such as five to six minutes (with heatingabove 900° F. (482° C.) for ten to twenty minutes, such as ten tofifteen minutes, such as ten to twelve minutes during the heatingcycle), with no significant degradation of the functional coating 16,e.g., with less than 5% loss of visible light transmission, such as lessthan 3% loss, such as less than 2% loss, such as less than 1% loss, suchas no loss of visible light transmission.

To form the laminated article 10 of the invention, the coated glass ply12 is positioned with the coated inner major surface 14 facing thesubstantially complimentary inner major surface 22 of the non-coated ply20 and separated therefrom by the polymeric layer 18. A portion, e.g. aband of about 2 mm in width, of the coating 16 end/or protective coating17 can be removed from around the perimeter of the first ply 12 beforelamination. The ceramic band 90 can be provided on one or both of theplies 12 or 20, e.g., on the outer surface 13 of the first ply 12, tohide the non-coated peripheral edge region of the laminated sidelightand/or to provide additional shading to passengers inside the vehicle.The first ply 12, polymeric layer 18 and second ply 20 can be laminatedtogether in any convenient manner, for example but not to be consideredas limiting, as disclosed in U.S. Pat. Nos. 3,281,296; 3,769,133; and5,250,146 to form the laminated sidelight 10 of the invention. An edgesealant 26 can be applied to the edge of the sidelight 10, as shown inFIG. 1.

Although the above method of forming the laminated sidelight 10 of theinvention utilizes an RPR apparatus and method, the sidelight 10 of theinstant invention may be formed with other methods, such as horizontalpress bending methods disclosed, for example, in U.S. Pat. Nos.4,661,139; 4,197,108; 4,272,274; 4,265,650; 4,508,556; 4,830,650;3,459,526; 3,476,540; 3,527,589; and 4,579,577.

FIG. 3 illustrates a monolithic article 100, in particular a monolithicautomotive transparency, incorporating features of the invention. Thearticle 100 includes a substrate or ply 102 having a first major surface104 and a second major surface 106. A functional coating 108 can beformed over at least a portion, such as the majority, e.g., all, of thesurface area of the first major surface 104. A protective coating 110 ofthe invention can be formed over at least a portion, such as themajority, e.g., all, of the surface area of the functional coating 108.The functional coating 108 and protective coating 110 can be formed inany desired method, such as those described above. The functionalcoating 108 and protective coating 110 define a coating stack 112. Thecoating stack 112 can include other coating layers or films, such as butnot limited to a conventional color suppression layer or a sodium iondiffusion barrier layer, just to name a few. An optional polymeric layer113, such as comprising one or more polymeric materials such as thosedescribed above, can be deposited over the protective coating 110 in anydesired manner.

The ply 102 can be of any desired material, such as those describedabove for the plies 12, 20 and can be of any desired thickness. In onenon-limiting embodiment for use as a monolithic automotive sidelight,the ply 102 can have a thickness of less than or equal to 20 mm, e.g.,less than about 10 mm, such as about 2 mm to about 8 mm, e.g., about 2.6mm to about 6 mm.

The functional coating 108 can be of any desired type or thickness, suchas those described above for the functional coating 16. In oneembodiment, the functional coating 108 is a solar control coating havinga thickness of about 600 Å to about 2400 Å.

The protective coating 110 can be of any desired material and have anydesired structure, such as those described above for the protectivecoating 17. The protective coating 110 of the invention can be formed inan amount sufficient to increase, e.g., significantly increase, theemissivity of the coating stack 112 over the emissivity of just thefunctional coating 108 alone. For one exemplary monolithic article, theprotective coating 110 can have a thickness of greater than or equal to1 micron, such as in the range of micron to 5 microns. In oneembodiment, the protective coating 110 increases the emissivity of thecoating stack 112 by at least a factor of 2 over the emissivity of thefunctional coating 108 alone (i.e., if the emissivity of the functionalcoating 108 is 0.05, the addition of the protective coating 110increases the emissivity of the resultant coating stack 112 to at least0.1). In another embodiment, the protective coating 110 increases theemissivity by at least a factor of 5, such as by a factor of 10 or more.In a further embodiment, the protective coating 110 increases theemissivity of the coating stack 112 to 0.5 or more, such as greater than0.8, e.g., in the range of about 0.5 to about 0.8.

Increasing the emissivity of the coating stack 112 maintains the solarenergy reflectance of the functional coating 108 (e.g., reflectance ofelectromagnetic energy in the range of 700 nm to 2100 nm) but decreasesthe thermal energy reflecting capability of the functional coating 108(e.g., reflectance of electromagnetic energy in the range of 5000 nm to25,000 nm). Increasing the emissivity of the functional coating 108 byformation of the protective coating 110 also improves the heating andcooling characteristics of the coated substrate during processing, asdescribed above in discussing the laminated article. The protectivecoating 110 also protects the functional coating 108 from mechanical andchemical attack during handling, storage, transport, and processing.

The protective coating 110 can have an index of refraction that is thesame or substantially the same as that of the ply 102 over which it isdeposited. For example, if the ply 102 is glass having an index ofrefraction of 1.5, the protective coating 110 can have an index ofrefraction of less than 2, such as 1.3 to 1.8, such as 1.4 to 1.8, e.g.,1.5±0.2. Additionally or alternatively, the protective coating 110 canhave a refractive index that is substantially the same as the refractiveindex of the polymeric layer 113.

The protective coating 110 can be of any thickness. In one monolithic;embodiment, the protective coating 110 can have a thickness of 1 micronor more to reduce or prevent a color variation in the appearance of thearticle 100. The protective coating 110 can have a thickness less than 5microns, such as in the range of 1 to 3 microns. In one embodiment, theprotective coating 110 can be sufficiently thick to pass theconventional ANSI/SAE 26.1-1996 test with less than 2% gloss loss over1000 revolutions in order to be used as an automotive transparency. Theprotective coating 110 need not be of uniform thickness across thesurface of the functional coating 108 but may have high and low spots orareas.

The protective coating 110 can be a single layer comprising one or moremetal oxide materials, such as those described above. Alternatively, theprotective coating 110 can be a multilayer coating having two or morecoating layers, such as described above. Each coating layer can compriseone or more metal oxide materials. For example, in one embodiment, theprotective coating 110 can comprise a first layer comprising aluminumoxide and a second layer comprising silicon oxide. The individualcoating layers can be of any desired thickness, such as described above.

The substrate with the coating stack 112 can be heated and/or shaped inany desired manner, such as that described above for heating the coatedblank of the laminated article.

The optional polymeric layer 113 can include one or more polymericcomponents, such as those described above for polymeric layer 18. Thepolymeric layer 113 can be of any desired thickness. In one non-limitingembodiment, the polymeric layer 113 can have a thickness greater than100 Å, such as greater than 500 Å, such as greater than 1000 Å, such asgreater than 1 mm, such as greater than 10 mm, such as in the range of100 Å to 10 mm. The polymeric layer 113 can be a permanent layer (i.e.,not intended to be removed) or can be a temporary layer. By “temporarylayer” is meant a layer intended to be removed, such as but not limitedto removal by combustion or washing with a solvent, in a subsequentprocessing step. The polymeric layer 113 can be formed by anyconventional method.

The monolithic article 100 is particularly useful as an automotivetransparency. As used herein, the term “automotive transparency” refersto an automotive sidelight, back light, moon roof, sunroof, and thelike. The “transparency” can have a visible light transmission of anydesired amount, e.g., 0% to 100%. For vision areas, the visible lighttransmission is preferably greater than 70%. For non-vision areas, thevisible light transmission can be less than 70%.

If the ply 102 with only the functional coating 108 were used as anautomotive transparency, such as a sidelight, the low emissivityfunctional coating 108 could reduce solar energy passing into theautomobile but could also promote a greenhouse effect trapping thermalenergy inside the automobile. The protective coating 110 of theinvention overcomes this problem by providing a coating stack 112 havinga low emissivity functional coating 108 (e.g., emissivity of 0.1 orless) on one side of the coating stack 112 and a high emissivityprotective coating 110 (e.g., emissivity of 0.5 or more) on the otherside. The solar reflecting metal layers in the functional coating 108reduce solar energy passing into the interior of the automobile and thehigh emissivity protective coating 110 reduces the greenhouse effect andpermits thermal energy inside the automobile to be removed.Additionally, layer 110 (or layer 17) can be solar absorbing in one ormore of the UV, IR, and/or visible regions of the electromagneticspectrum.

With respect to FIG. 3, the article 100 can be placed in an automobilewith the protective coating 110 facing a first side 114 of theautomobile and the ply 102 facing a second side 116 of the automobile.If the first side 114 faces the exterior of the vehicle, the coatingstack 112 will reflect solar energy due to the reflective layers presentin the functional coating 108. However, due to the high emissivity,e.g., greater than 0.5, of the coating stack 112, at least some of thethermal energy will be absorbed. The higher the emissivity of thecoating stack 112, the more thermal energy will be absorbed. Theprotective coating 110, in addition to providing increased emissivity tothe coating stack 112, also protects the less durable functional coating108 from mechanical and chemical damage. The optional polymeric layer113 can also provide mechanical and/or chemical durability.

Alternatively, if the first side 114 faces the interior of the vehicle,the article 100 still provides solar reflectance due to the metal layersin the functional coating 108. However, the presence of the protectivecoating 110 reduces thermal energy reflectance by absorbing the thermalenergy to prevent the thermal energy from heating the car interior toelevate its temperature and reduces the greenhouse effect. Thermalenergy from the interior of the vehicle is absorbed by the protectivecoating 110 and is not reflected back into the interior of the vehicle.

Although particularly useful for automotive transparencies, the coatingstack of the invention should not be considered as limited to automotiveapplications. For example, the coating stack can be incorporated into aconventional insulating glass (IG) unit, e.g., can be provided on asurface, either inner or outer surface, of one of the glass sheetsforming the IG unit. If on an inner surface in the air space, thecoating stack would not have to be as mechanically and/or chemicallydurable as it would if on an outer surface. Additionally, the coatingstack could be used in a seasonably adjustable window, such as disclosedin U.S. Pat. No. 4,081,934. If on an outer surface of the window, theprotective coating should be sufficiently thick to protect thefunctional coating from mechanical and/or chemical damage. The inventioncould also be used as a monolithic window.

Reduction of Visible Light Transmittance

In another aspect of the invention, the materials utilized for theprotective coating of the invention can also be used to chemically alteran underlying functional coating or coating layer to produce a coatedarticle having a different, e.g., reduced, visible light transmittanceupon heating of the coated article. This method can provide glasssuitable for use as privacy glass, such as for automobiles. For purposesof explaining this aspect of the invention, FIG. 9 discloses anexemplary coated article 180 having a substrate 200, e.g., glass, afunctional coating 202 deposited over at least a portion of thesubstrate 200, and a protective coating 204 of the invention depositedover at least a portion of the functional coating 202. A portion 208 ofthe functional coating 202 is specifically illustrated for purposes ofexplanation.

As described above, the functional coating 202 can be deposited over thesubstrate 200 by any conventional method, such as but not limited tospray pyrolysis, chemical vapor deposition (CVD), sol-gel, electron beamevaporation, or magnetron sputter vapor deposition (MSVD), just to namea few.

In the illustrated embodiment, the coating portion 208 includes a firstanti-reflective layer 210 which can comprise one or more films ofdielectric materials or anti-reflective materials, such as but notlimited to metal oxides, oxides of metal alloys, nitrides, oxynitrides,or mixtures thereof. The first anti-reflective layer 210 can betransparent or substantially transparent. Examples of suitable metaloxides for the first anti-reflective layer 210 include but are notlimited to oxides containing titanium, hafnium, zirconium, niobium,zinc, bismuth, lead, indium, tin, and mixtures thereof. These metaloxides can have small amounts of other materials, such as manganese inbismuth oxide, indium in tin oxide, etc. Additionally, oxides of metalalloys or metal mixtures, such as oxides containing zinc and to (e.g.,zinc stannate), oxides of indium-tin alloys, silicon nitrides, siliconaluminum nitrides, or aluminum nitrides, can be used. Further, dopedmetal oxides, such as antimony or indium doped tin oxides or nickel orboron doped silicon oxides can be used. The first anti-reflective layer210 can be a substantially single phase film, such as a metal alloyoxide film, e.g., zinc stannate, or can be a mixture of phases composedof zinc and tin oxides or can be composed of a plurality of metal oxidefilms, such as those disclosed in U.S. Pat. Nos. 5,821,001; 4,898,789;and 4,898,790.

In one non-limiting embodiment, the first anti-reflective layer 210 cancomprise a multi-film structure having a first metal alloy oxide filmdeposited over at least a portion of the substrate and a second metaloxide film deposited over the first metal alloy oxide film. In oneembodiment, the first anti-reflective layer 210 can have a totalthickness of less than or equal to 500 Å, e.g., less than or equal to300 Å, e.g., less than or equal to 280 Å, e.g. in the range of greaterthan 0 Å to 500 Å. For example, the first metal alloy oxide film canhave a thickness in the range of 100 Å to 500 Å, such as 150 Å to 400 Å,e.g., 200 Å to 250 Å. The second metal oxide film can have a thicknessin the range of 50 Å to 200 Å, such as 75 Å to 150 Å, e.g., 100 Å. Inone embodiment, the metal alloy oxide film can be a zinc/tin alloyoxide. The zinc/tin alloy can comprise zinc and tin, such as inproportions of 10 wt. % to 90 wt. % zinc and 90 wt. % to 10 wt. % tin.One suitable metal alloy oxide zinc stannate. By “zinc stannate” ismeant a composition of Zn_(x)Sn_(1-x)O_(2-x) where x varies in the rangeof 0 to 1. The metal oxide film can be a zinc containing film, such aszinc oxide. The zinc oxide film can include other materials to improvethe sputtering characteristics of the associated cathode, e.g., the zincoxide can contain 0 to 20 wt. % tin, e.g., 0 to 15 wt. % tin, e.g., 0 to10 wt. % tin.

A first infrared (IR) reflective film 212 can be deposited over thefirst anti-reflective layer 210. The first IR reflective film 212 can bean IR reflective metal, such as but not limited to gold, copper, silver,or mixtures, alloys, or combinations thereof. In one non-limitingembodiment, the first IR reflective film 212 can have a thickness in therange of 25 Å to 300 Å, e.g., 50 Å to 300 Å, e.g., 50 Å to 150 Å, suchas 75 Å to 100 Å, e.g., 80 Å.

A first primer film 214 can be deposited over the first IR reflectivefilm 212. The first primer film 214 can be an oxygen capturing material,such as titanium, that can be sacrificial during the MSVD depositionprocess to prevent degradation of the first IR reflective film 212during a sputtering process. The oxygen capturing material can be chosento oxidize before the material of the IR reflective film. In oneembodiment, the first primer film 214 can have a thickness the range of5 Å to 50 Å, e.g., 10 Å to 40 Å, e.g., 12 Å to 20 Å, 20 Å to 30 Å. Inone embodiment having two IR reflective films, e.g., two silvercontaining IR films, the individual primer layers can be greater than orequal to 10 Å, such as greater than or equal to 15 Å, such as greaterthan or equal to 20 Å. In one non-limiting embodiment for a functionalcoating comprising two silver containing IR reflective films, the total(i.e., sum of the) thickness for the two primer layers is in the rangeof 30 Å to 50 Å, such as 35 Å to 45 Å, such as 38 Å to 42 Å, such as 40Å, for a density of 4.3 grams/cm as calculated by x-ray fluorescence fora sputtered titania film.

Another (second) anti-reflective layer 218 can be deposited over thefirst primer film 214. The anti-reflective layer 218 can comprise one ormore metal oxide or metal alloy oxide films, such as those describedabove with respect to the first anti-reflective layer 210. In oneembodiment, the second anti-reflective layer 218 can have a first metaloxide film, e.g., zinc oxide, deposited over the first primer film 214.A second metal alloy oxide film, e.g., a zinc stannate film, can bedeposited over the first zinc oxide film. A third metal oxide film,e.g., another zinc oxide film, can be deposited over the zinc stannatefilm to form a multi-film layer. In one embodiment, each metal oxidefilm of the second anti-reflective layer 218 can have a thickness in therange of about 50 Å to 200 Å, e.g., 75 Å to 150 Å, e.g., 100 Å. Themetal alloy oxide film can have, a thickness in the range of 100 Å to500 Å, e.g., 200 Å to 500 Å, e.g., 300 Å to 500 Å, e.g., 400 Å.

The protective coating 204 can include the same materials as describedabove for the protective coating 17. For example, the protective coating204 can include a metal oxide, such as alumina, silica, indium oxide, oroxides or oxynitrides of metals, such as silicon nitride, siliconoxynitride, aluminum nitride, indium tin oxide, tin doped indium oxide,or similar materials or mixtures thereof that can act as a gas and/orvapor barrier as described below. The protective coating 204 can be ofany thickness. In one embodiment, the protective coating 204 can have athickness of greater than 20 Å, e.g., greater than 25 Å, e.g., greaterthan 50 Å, e.g., greater than 100 Å, e.g., greater than 150 Å, e.g.,greater than 200 Å, e.g., in the range of 50 Å to 5000 Å, e.g., 50 Å to250 Å. In another non-limiting embodiment, the protective coating 204can have a thickness in the range of 100 Å to 10 microns, including anyof the sub-ranges such as those described above for the protectivecoating 17.

As will be appreciated by one skilled in the art, a conventionalfunctional coating can have a plurality of these anti-reflectivelayer/infrared reflective film/primer regions. One exemplary coating isdisclosed in International Application No. PCT/US03/04127. However, thepresence of a protective coating 204 of the invention (functioning as agas and/or vapor barrier layer, e.g., an oxygen barrier) during heatingof the coated article 180, e.g., for bending or shaping, can result in achange, e.g., increase, in opacity or in a color change (darkening) ofthe coated article 180, e.g., a chemical change in the functionalcoating 202 which can reduce visible light transmittance. For example,in one embodiment in which the infrared reflective layer 212 includessilver and the first anti-reflective layer 210 includes a metal oxide oralloy oxide including tin, upon heating of the coated article to aconventional temperature sufficient to bend or shape the glass, theprotective coating 204 acts as a gas or vapor barrier to reduce, retard,or prevent the diffusion of atmospheric gas or vapor, e.g., oxygen,through the protective coating 204 and into the functional coating 202(at least during the bending or shaping process). In this event, it isbelieved that strong oxidizers in the functional coating 202, such astitanium, can scavenge oxygen from the other materials in the coatingstack. Should the oxygen be scavenged from the tin containing metaloxide anti-reflective layer 210 below the silver containing IR layer212, the resultant liberated tin metal can diffuse or move to the silvercontaining IR layer 212 and can combine or alloy with the silver metalto produce a silver tin combination or alloy. As used herein, the terms“alloy” or “alloying” can mean a combination of two or more materialsthat may or may not be a true alloy. This silver tin alloy can be darkerin color than the initial silver layer and can reduce the visible lighttransmittance through the article. This feature of the invention can beutilized to produce privacy-type glass. The presence of the tin silveralloy also reduces the conductivity of the silver layer.

This aspect of the invention could also be used to produce banded orshaded areas of lower visible light transmittance on a coated substrate.For example, a functional coating of the type shown in FIG. 9 could bedeposited over a substrate and then portions of the functional coatingcould be overcoated with a protective coating 204 (i.e., gas/vaporbarrier layer) of the invention as described above. The coated articlecould subsequently be heated to a temperature sufficient to cause thedarkening result described above and the functional coating under theprotective coating would become darker or less transparent to visiblelight and produce darkened or shaded regions on the article.

This feature of the invention, i.e., darkening of the functionalcoating, can be prevented or reduced by employing a material which makesthe material of the IR reflective film 212, e.g., silver, lesssusceptible to alloying with alloying material in the rest of thecoating, e.g., tin. For example, as shown in FIG. 10, an alloyprevention layer, e.g., a crystalline layer 220, such as a crystallinezinc oxide containing layer, can be positioned below the IR layer 212.This crystalline layer 220 has been found to prevent, retard, or reducethe combination or alloying of the silver with tin produced during aconventional heating operation in the presence of the protective layer.In the embodiment under consideration, it is believed that thecrystalline structure of the crystalline zinc oxide forces the silver tobe crystalline and to be oriented in a particular manner which makes thesilver less likely to alloy with tin.

Thus, to produce the darkening effect described above for the formationof privacy glass, the functional coating can contain a material that canahoy with material in the IR layer 212 to produce a darker (i.e., lesstransparent) combination and/or reduce visible light transmissionthrough the article. In one practice of the invention for producingprivacy glass, the protective coating functions as a gas or vapor, e.g.,oxygen, diffusion barrier during heating. A scavenger or getter in thefunctional coating having a higher reduction potential than the alloyingmaterial, e.g., tin, can draw oxygen away from the alloying material.The tin can then alloy with the silver, in the absence of an ahoyprevention layer, to form a darker area or area of lower visible lighttransmittance in the article.

While in the above exemplary embodiment the alloying material, i.e.,material liberated during heating, was tin and the material in the IRfilm was silver, it is to be understood that the invention is notlimited to coatings having this specific combination of materials. Thealloying material and IR material can be of any combination of materialssuch that upon heating of the coated article in the presence of theprotective coating (without an alloy prevention layer) the alloyingmaterial is liberated and can alloy with the IR material to change,e.g., decrease, light transmission, e.g., visible light transmission,through the article. For example, the functional coating can containmaterials (e.g., metals as oxides or metal alloys) containing materials,for example, antimony, bismuth, indium, and the like which can alloy orcombine with the material of the IR reflective layer to darken and/orchange the color of the functional coating.

Additionally, while the gas/vapor diffusion layer (protective coating)was shown in the above embodiment as being the outer layer of the stack,it could be an inner layer so long as it can function to prevent,retard, or moderate the diffusion of gas or vapor into the portion ofthe functional coating to achieve the results discussed above.Additionally, while the prevention layer described above was zinc oxide,it should be appreciated that the prevention layer is not limited tozinc oxide but can be any material which prevents, retards, or reducesalloying, combining, or reacting of the alloying material with the IRmaterial. For example, titania and/or zirconia can also act asprevention layers. Moreover, even if the prevention layer is zinc oxide,it need not be totally zinc oxide but could contain other materials,such as tin, so long as the prevention layer is crystalline andfacilitates or enhances the proper crystalline orientation of the IRmaterial, i.e., silver, to reduce or prevent the silver from alloyingwith tin. Additionally, the prevention layer does not necessarily haveto be crystalline so long as it functions to prevent or retardcombination of the materials that promote darkening of the coating.Additionally, varying the thickness of the prevention layer can affectthe degree of darkening. For example, as a general rule, with all elseremaining equal, the thinner the prevention layer the darker will be thecoating.

The visible light reflectance can differ with respect to the two sides(protective coating side and substrate side) of the article. Forexample, the visible light reflectance can be low in one direction andhigh or low in the other direction. In one example, the outer visiblelight reflectance (viewed from the protective coating side) can behigher than the inner reflectance (viewed from the substrate side). Inone embodiment, the outer visible light reflectance can be less than orequal to 25%, e.g., less than or equal to 20%, e.g., less than or equalto 15%, e.g., less than or equal to 10%, e.g., in the range of 10% to20%, e.g., about 15% and the inner reflectance can be less than or equalto 15%, e.g., less than or equal to 10%, e.g., less than or equal to 8%,e.g., in the range of 5% to 10%, e.g., about 8%. For automotiveapplications, the lower reflection side (whichever that may be) can beplaced to face the interior of the automobile. In similar manner, thereflected color of the article can differ between the two sides or bethe same.

The article 180 can also have a low visible light transmission, e.g.,less than or equal to 75%, e.g., less than or equal to 65%, e.g., lessthan or equal to 60%, e.g., less than or equal to 50%, e.g., less thanor equal to 40%, e.g., less than or equal to 30%, e.g., less than orequal to 20%.

The article 180 can also be high in infrared energy reflection, e.g.,greater than or equal to 60%, e.g., greater than or equal to 70%, e.g.,greater than or equal to 80%.

While the above described method of heating an article with a protectivecoating of the invention to combine or alloy various components of thefunctional coating is useful for forming the article 180, it is to beunderstood that if the characteristics of the alloyed coating aredesired, the functional coating could be initially deposited with thealloyed materials initially present (in the non-limiting embodimentdescribed above this would be the silver and tin alloy). In this event,the protective coating of the invention would add enhanced durability tothe darkened coating. This protective coating could also be heated sothe protective coating could be applied before heat treatment, such asbending or shaping of the substrate.

Illustrating the invention are the following examples which, however,are not to be considered as limiting the invention to theft details. Allparts and percentages in the following examples, as well as throughoutthe specification are by weight unless otherwise indicated.

Example 1

Several Samples of functional coatings with different protectivecoatings of the invention were prepared and tested for durability,scattered light haze developed after Taber abrasion, and emissivity. Thefunctional coatings were not optimized for mechanical or opticalproperties but were utilized simply to illustrate the relativeproperties, e.g., durability, emissivity, and/or haze, of afunctionally-coated substrate having a protective coating of theinvention. Methods of preparing such functional coatings are described,for example but not to be considered as limiting, in U.S. Pat. Nos.4,898,789 and 6,010,602.

Test samples were produced by overcoating different functional coatingsas described below (on common soda lime clear glass) with aluminum oxideprotective coatings incorporating features of the invention and havingthickness in the range of 300 Å to 1.5 microns. The functional coatingsused in the tests have high solar infrared reflectance andcharacteristic low emissivity and are comprised of multilayerinterference thin films achieved by depositing alternating layers ofzinc stannate and silver by magnetron sputtering vacuum deposition(MSVD). For the samples discussed below, typically two silver layers andthree zinc stannate layers were present in the functional coating. Thintitanium metal primer layers are also used in the functional coatings ontop of the silver layers to protect the silver layers from oxidationduring MSVD deposition of the oxide zinc stannate layers and to surviveheating to bend the glass substrate. The two functional coatings used inthe following examples differ mainly in the outermost thin layer of themultilayer coating, one being metallic Ti and the other being oxideTiO₂. Thickness of either the Ti or TiO₂ outer layer is in the range 10Å to 100 Å. Alternative examples which are equally applicable but whichwere not prepared are functional coatings without a Ti or TiO₂ outerlayer or different metallic or oxide outer layers. The functionalcoatings used for the examples having the thin Ti outer layer have ablue reflecting color after heating and with the TiO₂ outer layer have agreen reflecting color after heating. Other resulting reflecting colorsof functional coatings after heating which can be protected with aprotective coating of the invention can be achieved by changing thethickness of the individual silver and zinc stannate layers in thefunctional coating.

Thin or thick aluminum oxide protective coatings for the followingexamples were deposited by mid-frequency, bi-polar, pulsed dualmagnetron reactive sputtering of Al in an Airco ILS 1600, speciallymodified to power two of the three targets. Power was provided by anAdvanced Energy (AE) Pinnacle® Dual DC power supply and Astral®switching accessory, that converts the DC supply to a bi-polar, pulsedsupply. Glass substrates with the functional coating were introducedinto the Airco ILS 1600 MSVD coater having an oxygen reactiveoxygen/argon atmosphere. Two aluminum cathodes were sputtered fordifferent times to achieve the different thickness aluminum oxidecoatings over the functional coatings.

Three sample coupons (Samples A-C) were prepared and evaluated asfollows:

-   -   Sample A—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thick        clear float glass commercially available from PPG Industries,        Inc., of Pittsburgh, Pa.    -   Sample B—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thick        clear glass coupons having an experimental low emissivity        functional coating approximately 1600 Å thick with green        reflecting color produced by MSVD (as described above) and no        protective aluminum oxide protective coating were used as a        control sample.    -   Sample C—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thick        glass coupons having an experimental functional coating        approximately 1600 Å thick with blue reflecting color produced        by MSVD but further having a 1.53 micron thick aluminum oxide        (Al₂O₃) protective coating of the invention deposited over the        functional coating.

Replicate Samples A-C were then tested in accordance with a standardTaber Abrasion Test (ANSI/SAE 26.1-1996) and the results are shown inFIG. 4. Scratch density (SD) measurements after Taber for a given numberof cycles were determined by microscope measurements of the totalscratch length of all scratches in a square micron area using digitizingand image analysis software. The Sample C (protective coated) couponsshowed a lower scratch density than the Sample B (functionally coated)coupons. The Sample C coupons had about the same durability as theuncoated glass coupons of Sample A. The Taber results were obtained forthe “as deposited” protective coating, meaning the coated glass couponswere not post-heated after MSVD deposition of the protective coating. Itis expected that the scratch density results should improve (i.e., thescratch density for few Taber cycles should decrease) upon heating ofthe coated substrate due to increased density of the heated coatingstack. For example, the coated substrates could be heated from ambientto a maximum temperature in the range of 640° C. to 704° C. and cooledover a time period of about 10 mins to about 30 mins.

FIG. 5 shows the average scattered light haze versus Taber cycles (inaccordance with ANSI/SAE 26.1-1996) for replicate Samples A and C asdescribed above. Sample A is uncoated glass used as a control. Resultsindicate that the haze that develops for Sample C after 1000 cycles isclose to 2%, the minimum acceptable specified by ANSI for automotiveglazing safety. A modest improvement in the durability of the protectivecoating is expected to result in less than 2% haze after 1000 Tabercycles, exceeding the ANSI safety specification for automotive glazing.

FIG. 6 shows the effect of a protective overcoat of the inventiondeposited at different MSVD process vacuum pressures over two differentfunctional coatings. The Samples shown in FIG. 6 are 2 mm thick couponsof clear float glass with the following coatings deposited thereon:

-   -   Sample D—control sample; nominally 1600 Å thick blue reflecting        functional coating having no protective coating.    -   Sample E—control sample; nominally 1600 Å thick green reflecting        functional coating having no protective coating.    -   Sample F(HP)—the functional coating of Sample D plus an aluminum        oxide protective coating sputter deposited as described above at        an MSVD process vacuum pressure of 8 microns of oxygen and        argon.    -   Sample F(LP)—the functional coating of Sample D plus an aluminum        oxide protective coating sputter deposited as described above at        an MSVD process vacuum pressure of 4 microns of oxygen and        argon.    -   Sample G(HP)— the functional coating of Sample E plus an        aluminum oxide protective coating sputter deposited as described        above at an MSVD process vacuum pressure of 8 microns of oxygen        and argon.    -   Sample G(LP)— the functional coating of Sample E plus an        aluminum oxide protective coating sputter deposited as described        above at an MSVD process vacuum pressure of 4 microns of oxygen        and argon.

As shown in FIG. 6, as the thickness of the protective coatingincreases, the emissivity of coating stack also increases. At aprotective coating thickness of about 1.5 microns, the coating stack hadan emissivity of greater than about 0.5.

FIG. 7 shows the results of scratch density measurements after 10 cyclesTaber abrasion for Samples F(HP), F(LP), G(HP), and G(LP) describedabove. The control functional Samples D and E with no protective coatinghad initial scratch densities on the order of about 45 mm⁻¹ to 50 mm⁻¹.As shown in FIG. 7, the application of a protective coating of theinvention (even on the order of less than about 800 Å) improves thedurability of the resultant coating stack.

FIG. 8 shows the results of scratch density measurements after 10 cyclesTaber abrasion for the following Samples of blue or green reflectingfunctional coatings with aluminum oxide protective coatings 300 Å, 500Å, and 700 Å thick:

-   -   Sample H—the functional coating of Sample D plus an aluminum        oxide protective coating sputter deposited as described above by        MSVD.    -   Sample I—the functional coating of Sample E plus an aluminum        oxide protective coating sputter deposited as described above by        MSVD.

As shown on the right side of FIG. 8, heating the coating stack of theinvention improves the durability of the coating stack. The coatings onthe right side of FIG. 8 were heated by insertion in a 1300° F. oven for3 mins, and then removed and placed in a 400° F. oven for 5 mins, afterwhich the coated samples were removed and allowed to cool under ambientconditions.

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. For example, althoughin the preferred embodiment of the laminated article only one plyincludes a functional coating, it is to be understood that the inventioncould also be practiced with both plies having a functional coating orone ply having a functional coating and the other ply having anon-functional coating, e.g., a photocatalytic coating. Moreover, aswill be appreciated by one of ordinary skill in the art, the preferredoperating parameters described above can be adjusted, if required, fordifferent substrate materials and/or thicknesses. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

1. A laminated article, comprising: a first ply having a first majorsurface; a functional coating over at least a portion of the first majorsurface and having an emissivity value; a protective coating comprising35 wt. % to 100 wt. % alumina and 0 wt. % to 65 wt. % silica over atleast a portion of the functional coating to form a coating stack havingan emissivity, the protective coating configured to increase theemissivity of the coating stack over the emissivity of the functionalcoating alone; a second ply; and an interlayer located between the firstand second plies, with the protective coating facing the interlayer. 2.The article of claim 1, wherein the first and second plies are selectedfrom glass, plastic, and ceramic material.
 3. The article of claim 1,wherein the protective coating has a refractive index in the range of1.5 to 2.0.
 4. The article of claim 1, wherein the protective coatingincreases the emissivity of the coating stack to be in the range of 0.3to 0.9.
 5. An article, comprising: a substrate; a functional coatingover at least a portion of the substrate; and a protective coatingcomprising 35 wt. % to 100 wt. % alumina and 0 wt. % to 65 wt. % silicaover the functional coating, wherein the functional coating and theprotective coating define a coating stack and the protective coatingprovides the coating stack with an emissivity higher than the emissivityof the functional coating alone.
 6. The article as claimed in claim 5,wherein the substrate is selected from glass, plastic, and ceramic. 7.The article as claimed in claim 5, wherein the article is an automotivetransparency.
 8. The article as claimed in claim 5, wherein thesubstrate has a thickness of 2 mm to 20 mm.
 9. The article of in claim5, wherein the functional coating has an emissivity of 0.1 or less. 10.The article of claim 5, wherein the protective coating increases theemissivity of the coating stack by at least a factor of two with respectto the emissivity of the functional coating.
 11. The article of claim 5,wherein the protective coating increases the emissivity of the coatingstack by a factor in the range of 2 to 20 compared to the emissivity ofthe functional coating.
 12. The article as claimed in claim 5, whereinthe functional coating has an emissivity of 0.1 or less and the coatingstack has an emissivity of 0.5 or more.
 13. The article as claimed inclaim 5, wherein the emissivity of the coating stack is 0.5 to 0.8. 14.The article as claimed in claim 5, wherein the protective coating has athickness of greater than 1 micron.
 15. The article as claimed in claim5, wherein the protective coating has a thickness of less than 5microns.
 16. The article as claimed it claim 5, wherein the protectivecoating comprises 86 wt. % to 90 wt. % alumina and 10 wt. % to 14 wt. %silica.
 17. The article as claimed in claim 5, wherein the protectivecoating is solar absorbing in at least one of the UV, IR, or visibleregions of the electromagnetic spectrum.
 18. A monolithic automotivetransparency, comprising: a glass substrate; a functional coating overat least a portion of the glass substrate; and a protective coating overthe functional coating to form a coating stack, the protective coatingcomprising 35 wt. % to 100 wt. % alumina and 0 wt. % to 65 wt. % silicahaving a thickness in the range of 1 micron to 5 microns and providingthe coating stack with an emissivity of at least 0.5.
 19. Thetransparency as claimed in claim 18, wherein the protective coatingcomprises 70 wt. % to 90 wt. % alumina and 10 wt. % to 30 wt. % silica.